The invention pertains to a microwave apparatus for heating contained liquid, and more particularly for thawing a bag of frozen blood components.
The prevailing method of thawing bags of frozen blood components is to insert the bag into a warm water bath. While the warm water bath distributes heat over the entire surface of the bag it is quite time consuming and sometines introduces bacterial contamination into the bag. In order to overcome the bacterial contamination problem some users have put the bag of blood components into a second hermetically sealed bag before insertion into the warm water bath. This second bag however, can easily be ripped by the still frozen blood unit, and prevention of water contact cannot be guaranteed.
An interesting approach to thawing blood components is to use a microwave oven. A microwave oven particularly adapted for heating frozen blood components is shown in U.S. Pat. No. 4,336,435. This patent teaches a major modification to an existing microwave oven by penetrating the side of the oven with a shaft which is operated by a motor mounted exteriorly from the over cavity. The shaft extends into the oven cavity and has a holder for positioning a blood bag in a vertical position. When the motor is operated the blood bag is rocked and/or rotated during oven operation.
It is particularly important in thawing blood components by microwaves to ensure that the blood does not boil. Without proper movement or agitation of the blood, microwave energy will concentrate on one portion of the blood to cause over heating while other portions of the blood still remain frozen. It is therefore important in microwave heating to ensure that the thawed warmer portions of the blood are caused to flow over the frozen portions so as to distribute the heat and prevent portions of the blood from boiling. It is also desirable to provide an arrangement for heating frozen blood in a standard microwave oven so that the expense of the heating arrangement can be minimized. It is also important for the heating apparatus to position the bag of blood for maximum reception of microwave energy.